Experimenting with fake 3D projection

# TODO
* base rendering (segments/curves)
* make random spline course
    * svg
    * visualize
* click to render segment at position (approx segment binary search)
* stick to segment while driving
    * road bounding box
    * angle
    * future: splits?
* hills
* horizon adjustment
* non-circular tracks ⇒ infinite road at end segment?
* sprites
* multi-road
    * real-world impl: two/three roads, disable one or two
* multi-level
    * level-split segments
    * level-join segments